In present telecommunication systems, in particular systems for cellular and cordless radio telecommunications, transceivers operating at frequencies in the GHz Radio Frequency (RF) band are used.
It is known that electric or electronic components or apparatuses and devices in the vicinity of electromagnetic radiation sources can be driven into malfunctioning if subjected to certain levels of electromagnetic radiation.
To avoid as much as possible any unwanted influence of electromagnetic radiation from devices such as oscillators in transceivers for telecommunication or other devices operating in the RF band, it is known to shield such radiation sources by encasing the radiation source or the device such as a transceiver incorporating the radiation source in a suitable housing. Such a housing is usually formed of conductive materials having an ability to concentrate high levels of magnetic flux. Accordingly, the electromagnetic radiation is prevented from leaving the housing.
On the other hand, it is also possible to encase an electric or electronic component which is sensitive to electromagnetic fields, such to prevent that any magnetic, electric or electromagnetic fields can reach the component through its encasing. Housings for shielding electromagnetic radiation are also known as Faraday cages.
U.S. Pat. No. 5,339,222 discloses a two-part electromagnetic radiation shielding housing for receiving a complete PCB.
GB-A-2,285,181 discloses a two-part shielding device for mounting at a PCB such that in use, a component requiring shielding is completely surrounded and enclosed by the shielding device and a signal ground layer of the PCB to which the device is electrically connected. The component can be either an electromagnetic radiation source or a component which is vulnerable to electromagnetic fields.
With the present trend towards using frequencies in the GHz range and due to increasing governmental regulations on electromagnetic stray field levels of devices such as mobile or cordless telephones and (small) base stations for indoor use, the presently available shielding devices are not suitable to meet future demanding ElectroMagnetic Compatibility (EMC) requirements.